Recording elements in which information is recorded by thermally deforming an optical recording layer are known. Such elements are useful in rapidly recording large amounts of digital information in a small area. These elements are also useful in recording video information.
Recording on an optical recording element is accomplished by a beam of high energy-density radiation such as a laser beam. The laser beam is focused onto the surface of the optical recording layer of the element. The recording layer absorbs energy from the laser so that a small portion of the layer is deformed. The deformation may be in the form of pits, holes or other changes in the material. This technique of optical recording on a heat-deformable recording layer is usually referred to in the optical recording art as "ablative recording".
Generally, there is continuous relative motion between the laser beam and the layer so that as the laser is pulse modulated, discrete deformations of varying sizes are created in the layer. The sizes and spacing of these deformations constitute the encoded information. A variety of materials have been proposed for use for the heat-deformable recording layer.
It is also known to overcoat the heat-deformable optical recording layer for a variety of purposes. For example, during the ablative recording process, a portion of the optical recording layer is removed in the form of a vapor which condenses and rains back upon the recording layer creating the potential for unwanted noise. To overcome this problem, U.S. Pat. No. 4,069,487 disclosed protective overcoats of ceramic material. These overcoats range in thickness of from 0.15 to 10 .mu.m.
The problem is that the relatively thick overcoats described in U.S. Pat. No. 4,069,487 have a deleterious effect upon the laser write sensitivity, and upon carrier-to-noise ratio (CNR) and recording linearity of recorded information in ablative materials. This deleterious effect impedes the use of relatively inexpensive low power diode lasers now being considered for use in optical recording systems.